Thermoquad rebuilt and tuning

Hello,

my Thermoquad is leaking. So I want to buy a rebuilt kit.
I also found a strip kit here in Germany.

My engine is a stock 400 with recurved distributor, dual exhaust, edelbrock performer intake.

I thought about using tuning parts when rebuilding it. But what rods and jets should I use? What else is important to know?

I really like my Thermoquad so I want to keep it.

EDIT:

My TQ has the number 9077S

I would start with the stock rods and jets and tune as or if needed from that point.

I have nothing to compare with.
When I built in the stock rods and jets I wouldn't know, if I need to go with bigger jets or smaller rods.

The rods/jets are going to be altering the air/fuel ratio. So once it's back together, with whatever rods/jets you have, you will likely want to read the plugs or even better, stick a wideband o2 sensor on the car and see where you are at.

The specs are primary jet- .098 secondary jets- .143 metering rods # 2159

Ok. I have access to an o2 sensor.
If it is just slightly off, would it be possible or recommended to just "screw" the rods up or down with the screw on top of the carburetor?

Primary jets are numbered, last three digits of the number relates to the orifice size directly. For instance, a primary jet 4095 is .095-inch or a 4101 measures .101-inch. Similarly, the last three digits of a secondary jet equates to the size as a fraction of an inch. A 5110 jet measures .110-inch, while a 5143 measures .143-inch.

Rod No. Econ Mid Power
615 .059 - .040
616 .064 - .030
655 .062 - .040
1937 .070" .046 .040
1938 .071 .051 .040
1939 .070 .058 .040
1940 .072 .060 .045
1941 .073 .061 .045
1950 .068 .057 .040
1961 .066 .056 .045
1962 .067 .055 .045
1965 .069 .061 .045
1966 .067 .052 .045
1994 .068 .043 .035
1995 .066 .040 .035
1996 .069 .048 .035
1997 .067 .045 .035
1998 .070 .057 .040
1999 .068 .054 .040
2000 .066 .054 .035
2001 .064 .051 .035
2002 .065 .052 .040
2003 .063 .049 .040
2004 .067 .058 .040
2005 .065 .055 .040
2014 .069 .054 .040
2020 .066 .052 .045
2024 .066 .054 .040
2086 .069 .061 .040
2091 .074 .064 .040
2103 .069 - .045
2109 .069 .061 .045
2110 .069 .053 .040
2127 .074 .065 .040
2132 .074 .060 .040
2144 .06.0 61 .050
2145 .069 .061 .055
2153 .067 - .055
2154 .069 .061 .055
2159 .070 .062 .040
2173 .072 .057 .040
2174 .070. 055 .038
2179 .074 .066 .042
2195 .070 .062 .045
2210 .069 - .045
2211 .0715 .064 .040
2271 .070 .062 .035
2272 .070 .059 .038
2273 .065 .056 .045
2278 .069 - .048
2293 .066 - .055
2298 .066 .054 .040
2326 .066 .054 .048
2328 .072 .062 .045
2339 .060 - .040
2340 .075 - .040
2342 .066 .052 .035
2354 .070 .055 .033
2359 .072 .054 .045
2360 .070 - .050
2363 .070 .059 .038
2375 .070 .058 .040
2377 .066 .054 .040
2382 .073 - .054
2385 .069 - .053

with an A/F meter shoot for an average 13.5 air/fuel ratio

thank ou guys for your answers.
Mileage is not important. I want to go for maximum power.

Ya.. shoot for the 13.5 average number. TQ's don't like to be run overly rich Good luck!

I have to ask this, even if it sounds dumb and I might even know the answer.
But the car is over 40 years old and that kind of engine is not "standard" here in germany. So I better ask even stupid questions.

I get that you say 13.5 average. But is 13.5 more important at certain rpm or wot?
Maybe 13.5 at idle, then it get's leaner/richer and as rpm gets higher it(should) go back to 13.5 and at wot way over it?
so I could set 13.5 at idle or high rpm without secondaries.

The guy with the O2 Sensor is a specialist but we have (in normal cases) strict emission laws so (normally) theres no question at what point it has to have what AFR.
And mostly it is just control and not tuning.

EDIT:
Maybe I have got something wrong, writing a bit complicated (bad english) or just start to think too much.
The help I get from you guys as always very good.

Shoot for 13.5 to 14 for idle, ideally you want to hold that or go a little leaner off idle to cruise like 14 to 14.5. Wot about 12.5 to 13

Okay thanks a lot guys.

So I will rebuilt my TQ, then set idle by doing the basic tuning with the front screws to the point where the enginge does not rev faster. Than set it to about 700 to 800 rpm. Than hooking up the O2 sensor and measure at some points and maybe use a smaller metering rod and control the idle mixture with the front screws?

with the OE pri jet being a .098" I'd K.I.S.S. and try a .101 and set the height of the metering rod tree at the OE spec for a start (unless someone advises otherwise) and that'll get you off to a very good start by richening the power and cruise circuits a moderate amount

The 9077 is a Lean Burn carb, you might want to find an earlier one.

I have a new question, but it is a bit hard to explain in english.

On the very top of the TQ there ist that little screw for adjusting the metering rods.
over that screw there is normally that little metal thing with a hole in it so that you can reach the screw.
That thing is broken on my carburetor. the top part is missing (broken off). but the lower part of it exists and was holding down that whole metering rod part.
So two questions:
- Is that okay.
- was it right, that it was holding down the metering rods?

EDIT:
I forgot to ask about the buckets under the main wells.


The sealing material is normally oozing out (is that the right word). On my TQ it is not at some areas, because it broke off (it is really hard).
Should I reseal them? And if so, can I just rip em apart?

EDIT 2:
I just looked at some pictures and videos and all of them had the screw for the metering rods a the same level as the top of the piston. Mine was a fair bit over it (leaner?).
I know that my TQ never was adjusted right and all, that's why I am rebuilding it.
But that is a bit strange.

To adjust the metering rod assembly, first bottom the piston assembly with the fast idle cam off/choke open. Then back off the center adjuster slot counter-clockwise until the assembly stops dropping. The keeping the piston assembly bottomed, start turning the assembly clockwise and as soon as you feel the assembly start to move up, go 1.5 turns clockwise. To richen the main(cruise)circuit, turn the piston screw clockwise but be sure you count exactly how much you turn it. It should take less than 2 full turns to see any change in performance. This will usually get rid of any road speed hot weather surging in most cases.

The broken tang metal tang holding the metering rod assembly is a problem. Replace it.

As long as the wells aren't leaking leave them alone. Easy to test if they are, put fluid in it overnight and see if it wet on the bottom the next day.

Here in germany it is a bit hard to find a replacement for the metal tang.
Just the top with the hole is missing. the bottom is still intact. Is the top just for the case, that the metering rod assembly pushes out, so it would stop it?

Yah it stops it's travel so it doesn't pop out. Should be easy to make that piece if need be.

I thought about making one, too. Will do that.

Now the stupid question: why are there 2 thin and one thick flange gaskets in the rebuild kit?

Probably a universal kit covering different applications. Lean Burn, etc.

At first I thought the thick one is like a spacer to keep the carb cool and the thin ones are the real gaskets.
Is the thick one ok with the whole "keeps the carb cooler"-thing in mind?

Should be fine.

just the thick one or all three. I don't get that there are two thin ones.

Another thing is the bowl vent.
Until now it wasn connected and sealed with a screw in a hose.
I have that charcoal thing in the front (which seems fully connected).

Is it critical to connect the bowl vent somewhere?

Just the thick one. never stack gaskets. Bowl vent is for emissions, so fuel vapors don't escape into the atmosphere. Hook it to the charcoal cannister if you want.

Just remember if you hook you carb bowl vent to the canister you need the canister system working so the vapors stored in the canister get purged out. You dont want the canister to fill with fuel vapors and not have them purged out or then the vapors will back up and make it hard to start on hot soaks and flood real easy. Ron

I can not guarantee, that the system and/or the canister work porperly.

Is it ok to leave the vent disconnected and sealed?

So now I am finished doing the rebuild. Took a bit longer, because I had to seal two cracks in the bowl and seal the primary wells.

At first I did tuning by ear to get it streetable. Then drove to a shop with an O2-sensor.
That thing only shows Lambda not air fuel ratio.
Although I turned the idle screws simmetrically, the right bank ran richer.
Now I have both banks on 0,91 Lambda. And when opening the throttle, it holds it there almost all the time.